Disc type center cutter for a boring machine

ABSTRACT

A fixed shaft is mounted on the cutterhead to extend across the rotary axis of the cutterhead. A plurality of independently freely rotating disc cutter wheels are mounted on said shaft at different radial spacings from the cutterhead axis. The cutterhead carries additional disc cutters spaced radially outwardly from the center cutter assembly. All disc cutters include circumferential cutting edges which cut concentric kerfs in the rock at the tunnel face and sloping breaker surfaces on opposite sides of the cutting edge for crushing and dislodging the rock between the kerfs. The centermost disc cutter of the center cutter assembly includes a radially inwardly facing breaker surface which crushes and dislodges the material within the kerf cut by said centermost disc cutter. The disc cutter wheels have parallel radial side faces. The wheels are mounted for rotation by plain bearings or bushings which carry the radial loads. Washer-like plain radial bearings are provided outwardly of each of the side faces to carry the thrust loads. A seal ring presenting a radial face of hard material against the radial side face of the cutter wheel surrounds each thrust bearing. A ring of elastomeric material serves to cushion the seal member and urge it positively into contact with the side face of the cutter wheel.

United States Patent [1 1 Crane [451 Sept. 4, 1973 [54] DISC TYPE CENTERCUTTER FOR A BORING MACHINE [75] Inventor: Clayton [1. Crane, Mercerisland,

Wash.

[73] Assignee: The Robbins Company, Seattle,

Wash.

22 Filed: Nov. 1, 1971 211 App]. No.: 194,217

[52] US. Cl 175/364, 175/352, 175/358,

175/372, 175/376, 299/86 [51] Int. Cl. E21b 9/08, E2lb 9/12 [58] Fieldof Search... 175/62, 334, 351,

m y xami qrwpavis fli li wn A ttorney-George M. Cole, Delbert J. Barnardet a].

[5 7] ABSTRACT A fixed shaft is mounted on the cutterhead to extendacross the rotary axis of the cutterhead. A plurality of independentlyfreely rotating disc cutter wheels are mounted on said shaft atdifferent radial spacings from the cutterhead axis. The cutterheadcarries additional disc cutters spaced radially outwardly from thecenter cutter assembly. All disc cutters include circumferential cuttingedges which cut concentric kerfs in the rock at the tunnel face andsloping breaker surfaces on opposite sides of the cutting edge forcrushing and dis lodging the rock between the kerfs. The centermost disccutter of the center cutter assembly includes a radially inwardly facingbreaker surface which crushes and dislodges the material within the kerfcut by said centermost disc cutter.

The disc cutter wheels have parallel radial side faces. The wheels aremounted for rotation by plain bearings or bushings which carry theradial loads. Washer-like plain radial bearings are provided outwardlyof each of the side faces to carry the thrust loads. A seal ringpresenting a radial face of hard material against the radial side faceof the cutter wheel surrounds each thrust bearing. A ring of elastomericmaterial serves to cushion the seal member and urge it positively intocontact with the side face of the cutter wheel.

11 Claims, 5 Drawing Figures DISC TYPE CENTER CUTTER FOR A BORINGMACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention relates to improvements in rock boring machines, andin particular to a new disc cutter assembly for cutting the rock at thecenter region of the rock face, and to improved bearing and seal.assemblies for disc type rock cutters.

2. Description of the Prior Art US. Pat. No. 3,232,670, granted Feb. I,1966 to Richard J. Robbins and Douglas F. Winberg discloses a typicalcutter arrangement on the cutterhead of a rock boring machine. Suchcutterhead includes a plu rality of disc cutter assemblies positionedfor cutting concentric kerfs in the rock. The disc cutters includesloping breaker surfaces flanking circumferential cutting edges. Thesebreaker surfaces serve to fracture and dislodge the rock materialbetween the kerfs. The center region of the cutterhead carries atri-cone cutter assembly which serves to grind away the material at theimmediate center of the rock face. One problem with this type of anarrangement is that the tri-cone cutter is inefficient unless it isrotated at a speed much faster than the disc cutters can be rotated.When rotated at low speeds the tri-cone cutter assembly wears out fast.Also, the tri-cone cutter assembly is subjected to lateral forcesimposed by the breaker surface of the innermost disc cutter wheel. Ithas been proposed to drive the tricone cutter assembly at a higher speedthan the rest of the cutterhead, or to replace such tri-cone cutter witha pattern of drag bits. However, neither of these arrangements have beensatisfactory, particularly when the rock to be cut is quite hard.

SUMMARY OF THE INVENTION According to the present invention, the centerregion of the rock face is cut by a disc cutter. The use of a disccutter at the center region is made possible by the employment of asupport shaft for the cutter wheel which extends laterally across therotational axis of the cutterhead. The shaft is made long enough tosupport a plurality (e.g., three) of disc cutter wheels. The next twodisc cutter wheels are mounted onto the cutterhead by independentmounting means spaced laterally outwardly from the center cutterassembly on the opposite sides thereof. This arrangement makes itpossible to start with a disc cutter wheel positioned to cut a firstkerf closely adjacent the rotational center of the cutterhead and thenprovide additional disc cutter wheels outwardly therefrom which areappropriately spaced apart in the radial direction to provide thenecessary minimum distance between kerfs to render the disc cutterseffective. The centermost disc cutter wheel includes s sloping breakersurface radially inwardly of its cutting edge which serves to crush anddislodge the material immediately surrounding the rotational axis of thecutterhead.

The necessary close radial spacing of the cutter wheels at the centerregion of the cutterhead is in part made possible by novel bearing andseal assemblies of this invention. According to the invention, each disccutter wheel of the center cutter assembly is mounted on a plain orsleeve type bearing or bushing for independent rotation about a commonsupport shaft. Each disc cutter wheel includes a pair of parallel,radial side surfaces and washer like plain thrust bearing which makecontact with radial inner portions of the side faces. The mounting meansfor the cutter wheels comprises an annular cavity or grooveconcentrically surrounding each thrust bearing. A seal ring is housed ineach such groove and is cushioned and urged axially towards its sidesurface of the cutter wheel by a backup elastomeric ring. The sealmember includes a hard radial face which is in sliding engagement withthe side face of the cutter wheel. This support bearing and sealarrangement requires a minimum of axial space and makes relatively closespacing of the cutter wheels possible. Also, the mounting of theinnermost plurality of cutter wheels on a single support shaft resultsin shaft support on each side of each disc cutter wheel.

These and other features, advantages and characteristics of the earthboring equipment of the invention will be apparent from the followingdetailed description of a typical and therefor nonlimitive embodiment ofthe invention, and from the accompanying illustrations.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a front elevational view ofan earth boring machine, showing a typical pattern of concentric circlecutting roller disc cutters on the cutterhead, and showing the centerdisc cutter assembly of this invention;

FIG. 2 is an isometric view of the center region disc cutter assembly,taken from above and looking toward one end and one side thereof;

FIG. 3 is an enlarged scale view of the central region of thecutterhead, showing the center cutter assembly in front elevation andshowing a surrounding group of additional roller cutters in reference;

FIG. 4 is a view of the center cutter assembly partially in bottom planand partially in longitudinal section, taken substantially along line 44of FIG. 3; and

FIG. 5 is a fragmentary enlarged scale sectional view in the seal regionof one of the disc cutters.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, the centercutter assembly 10 is shown to comprise three roller disc cutters I2,l4, 16 which are supported for independent free rotation on a singleelongated support shaft 18 (FIG. 4). The longitudinal axis x of shaft 18is directed across the longitudinal center line or rotational axis c ofthe cutterhead CH. Shaft axis x intersects cutterhead rotational axis cat a location which is axially between roller cutter 12 and rollercutter 14, but closer to roller cutter I2 then to roller cutter l4.Owing to this arrangement, the circumferential cutting edge 20 of cutterdisc I2 travels a relatively small circle 22. The cutting edge or apex24 of disc cutter 14 travels a slightly larger diameter circle 26. Thecutting edge 28 of disc cutter 16 travels a third and still largerdiameter circle 30. The circular paths 22, 26, 30 are concentricallybased about the cutterhead axis c. A plurality of additional cutterassemblies 32, 34 and 36 are arranged on the cutterhead CH to cutadditional concentric circles surrounding the inner cutter edge paths22, 26, 30.

Referring to FIGS. 2 and 4, the center cutter assembly 10 is shown tocomprise a mounting block having a base 38 which is bolted or otherwisefirmly secured to the cutterhead CH. The mounting block 38 includesmeans forming a support for common shaft 18 on each side of all three ofthe cutter discs 12, 14, 16. By way of typical and therefore nonlimitiveexample, the mounting block may comprise upwardly opening saddlesoutwardly of disc cutter 16, between disc cutters 12 and 16, and alsobetween disc cutters 12 and 14. These saddles, designated 40, 42 44 inFIG. 2, may be generally similar to the saddles at the opposite ends ofthe cutter mounting frame shown by FIGS. 1 and 2 of U.S. Pat. No.3,216,513, granted to Richard J. Robbins and Douglas F. Winberg on Nov.9, 1965.

In the illustrated embodiment the shaft 18 is provided with an enlargedhead portion 46 having a flat lower edge surface 48 which mates againsta flat upwardly directed surface provided on the near end portion ofbase 38. When the opposite end portion of the shaft 18, and the twointermediate portions of the shaft 18 between the cutters 12, 16, andl2, 14 are resting in the saddles 40, 42, 44, the flat head surface 48is resting on the base surface 50. The saddles 40, 42, 44 are providedwith retainer caps 52, 54, 56, respectively, which are secured to thesaddles 40, 42, 44 by machine bolts 58 or the like.

Each disc cutter 12, 14, 16 includes a pair of parallel radial sidefaces 60, 62 and a right cylindrical center opening 64. Each cuttingedge or apex 20, 24, 28 is flanked by a pair of sloping breaker surfaces66, 68. In the illustrated embodiment the angle a between the breakersurfaces 66, 68 is about 90 and the angle b between each surface 66, 68and the intersecting radial side surfaces 60, 62 is about 135. Ofcourse, these values are variables and in other installations might bedifferent.

According to the invention, an annular plain or sleeve bearing orbushing 70 supports each cutter disc 12, 14, 16 for independent rotationabout the shaft 18. A plain washer or annular disc like thrust bearing72 is provided on each side of each disc 12, 14, 16. Dowel pins 74,serving as locator pins for the thrust bearings 72, are inset intosockets formed therefor in either the shaft retainer caps 52, 54, 56 orthe saddles 40, 42, 44. As best shown by FIG. 5, an axial opening 76 isformed in each thrust bearing 72. Each locator pin 74 includes an outerend portion which projects only partially into the opening 76.

By way of example, the bearings 70, 72 may be made from a molybdenumdisulfide impregnated refactory metal composite material, such as a typedisclosed in U.S. Pat. No. 3,479,289, granted Nov. 18, 1969, to Jan. W.Van Wyk. Such seals comprise an annular seal ring 78 having a radialseal face 80 which is biased axially into contact with the radial sideface 60 or 62 of the cutter wheel l2, 14, 16 by means of an annular ringof an elastomeric material. Seal ring member 78 may be constructed froma suitable metal, ceramic or cermet, or may be of a compositeconstruction (e.g., a ring body of a first material and a seal face of aharder second material).

The seal members 78, 82 are located inside of annular grooves 84 whichare formed in the side face of the particular mounting structure facingeach cutter side face 60, 62. Referring to FIG. 4, at the right end ofthe view the groove 84 for the seal members 78, 82 is formed in theinside face of the head member 46. The lower portions of the othergrooves 84 are formed in the side faces of the saddles 40, 42, 44 andthe upper portions of such grooves 84 are formed in the side faces ofthe retainer members 52, 54. 56.

The radial bearings 70, the thrust bearings 72, and the saddle andretainer member mounted seal elements 78, are assembled. Then the shafthead mounted seal element 78, 82 are installed and the shaft 18 isinserted through the center of the assembly, including through thebearings 70. An O-ring'seal element 86 is located within an annulargroove formed in the end of shaft 18 opposite the head 46. This sealring 86 seals between the shaft 18 and the surrounding passageway formedby the saddle 40 and the retainer member 52.

A radial faced shoulder 88 is formed by portions of the saddle 40 andthe retainer member 52. Saddle 40 and retainer member 52 also include aninwardly tapering frusto-conical socket leading into the shoulder 88. Ashaft retainer disc or plate 92 is set into the socket 90. One or moremachine bolts 94 extend through openings in the plate 92 and thread intointernally threaded bores 96 formed in the shaft 18. The length of shaft18 is such that when the bolts 94 are tightened the end surface 98 ofthe shaft 18 is located slightly axially inwardly of the shoulder 88.Owing to this arrangement, the bolts 94 can be tightened for the purposeof drawing the head 46 into tight contact with bearing member 72 andretainer disc 92 into tight contact with the shoulder 88.

Although shown in combination with the center cutter assembly 10, theabove-described bearing, seal and mounting features are improvements indisc cutter technology which may be used in other disc cutterinstallations as well.

In operation, the cutterhead CH is rotated by a suitable drive mechanism(not shown). As it rotates, the disc cutters 12, 14, 16 of the centercutter assembly travel along the concentric circular paths 22, 26, 30,and the other cutters 34, 36 travel along other concentric circularpaths spaced outwardly from the center cutter assembly 10. The cuttingedges of the cutters l2, 14, 16, 34, 36 cut kerfs in the material beingmined as they rotate, and the sloping breaker surfaces 66, 68, etc.exert forces on the rock between the kerfs, tending to fracture anddislodge such material. The breaker face 68 of cutter wheel 12 isrotated about the cutterhead axis 0 and serves to fracture and dislodgethe rock material at the axis region.

From the foregoing, various further modifications, componentarrangements and modes of utilization of the rock cutting equipment ofthis invention will be apparent to those skilled in the art to which theinvention is addressed within the scope of the following claims.

What is claimed is:

1. In a rock boring machine including a cutterhead mounted for rotationabout an axis, center cutter means comprising a disc cutter wheel havinga circumferential cutting edge flanked by a pair of sloping rock breakersurfaces intersecting at the cutting edge, and means mounting said disccutter wheel on said cutterhead with its cutting edge spaced radiallyclose to said axis and oriented to cut a kerf concentrically surroundingsaid axis, with the radially inner rock breaker surface of such wheelbeing located close enough to said axis to effectively fracture all ofthe rock located radially inwardly of said kerf, said means comprisingan elongated fixed shaft extending across the cutterhead andintersecting the axis of rotation of the cutterhead, and shaft supportmeans on each side of said center cutter wheel.

2. The combination of claim 1, further comprising a plurality ofadditional disc cutter wheels mounted on the cutterhead and oriented tocut concentric kerfs surrounding the kerf cut by the inner cutter wheel,and each including a pair of sloping rock breaker surfaces flanking itscutting edge, said surfaces serving to fracture the rock between kerfs.

3. The combination of claim 1, wherein said shaft supports at least oneadditional disc cutter wheel which is independently mounted for freerotation about such shaft.

4. The combination of claim 3, wherein each said disc cutter wheelcomprises a pair of parallel radial side faces, such cutter wheels aremounted for independent free rotation about the shaft by an annularsleeve type bearing, and an annular radial thrust seal contacts theradial inner portion of each cutter wheel side face, and a seal memberconcentrically surrounds each said thrust washer, each seal memberhaving a radial seal face in sliding sealing contact with the side faceof the cutter wheel.

5. The combination of claim 4, wherein each seal member is provided withan annular ring of elastomeric material between it and a portion of themounting means, for cushioning the seal ring and axially urging it intocontact with the side face of the cutter wheel.

6. In a rock boring machine including a cutterhead mounted for rotationabout an axis, a center cutter assembly comprising:

a fixed shaft extending across the axis of rotation of the cutterhead, afirst disc cutter wheel mounted for free rotation about said shaft at alocation radi ally outwardly from said axis of rotation, a second disccutter wheel mounted for free rotation about said shaft at a locationspaced on the opposite side of said axis of rotation and radiallyoutwardly from said axis a further distance than said first disc cutterwheel, each of said disc cutter wheels comprising a circumferentialcutting edge oriented to cut a kerf along a circular path surroundingthe axis of rotation, and sloping rock breaker surfaces flanking saidcutting edge, with the radially inward breaker surface of the first disccutter wheel being spaced close enough to the axis of rotation toeffectively fracture the center region rock located inside the kerfestablished by such disc cutter wheel, and shaft support means on eachside of each said disc cutter wheel.

7. The combination of claim 6, further comprising a third disc cutterwheel mounted for free rotation on said shaft radially outwardly of saidfirst disc cutter wheel, said third disc cutter wheel being spacedradially outwardly from the axis of rotation a distance fruther than thesecond disc cutter wheel, and means supporting said shaft on each sideof said third disc cutter wheel.

8. The combination of claim 7, further including a fourth disc cutterwheel and mounting means therefor situated laterally outwardly from anintermediate portion of said center cutter assembly, including a fixedshaft extending radially of the cutterhead and substantially at a rightangle to the shaft of said center cutter assembly, said fourth disccutter wheel being mounted for free rotation about said second shaft toform a kerf radially outwardly adjacent the kerf cut by the third disccutter wheel.

9. The combination of claim 8, further comprising a fifth disc cutterwheel spaced laterally outwardly from said center cutter assembly on theside thereof opposite the fourth disc cutter wheel, and including afixed shaft mounted on said cutterhead to extend radially of thecutterhead and substantially at a right angle to the axis of the centercutter assembly shaft and substantially coaxially with the shaft for thefourth disc cutter wheel, said fifth disc cutter wheel bieng mounted forfree rotation about its shaft so as to cut a kerf radially outwardlyadjacent the kerf cut by the fourth disc cutter wheel.

10. A rock cutting assembly .comprising a fixed shaft, 7

a disc cutting wheel mounted for free rotation on said shaft, said wheelincluding a pair of generally radial side faces, a circumferentialcutting edge, and a pair of rock breaker surfaces flanking said cuttingedge and intersecting the radial side faces of said wheel, mountingmeans for said shaft including a member disposed axially outwardly ofeach said radial side face, each said member including an annular groovetherein opening towards its side face of the disc cutter wheel, anonrotating seal member inside each said groove, and an elastomericmaterial serving to urge each seal member axially towards its radialface of the disc cutter wheel, said seal member including a radial sealface making sliding sealing contact with the radial face of the disccutter wheel.

11. The rock cutter assembly of claim 10, comprising a sleeve type plainbearing mounting said disc cutter wheel for free rotation about theshaft, and an annular radial thrust bearing supported axially outwardlyof each radial side face of the disc cutter wheel, radially inwardly ofthe seal members.

1. In a rock boring machine including a cutterhead mounted for rotationabout an axis, center cutter means comprising a disc cutter wheel havinga circumferential cutting edge flanked by a pair of sloping rock breakersurfaces intersecting at the cutting edge, and means mounting said disccutter wheel on said cutterhead with its cutting edge spaced radiallyclose to said axis and oriented to cut a kerf concentrically surroundingsaid axis, with the radially inner rock breaker surface of such wheelbeing located close enough to said axis to effectively fracture all ofthe rock located radially inwardly of said kerf, said means comprisingan elongated fixed shaft extending across the cutterhead andintersecting the axis of rotation of the cutterhead, and shaft supportmeans on each side of said center cutter wheel.
 2. The combination ofclaim 1, further comprising a plurality of additional disc cutter wheelsmounted on the cutterhead aNd oriented to cut concentric kerfssurrounding the kerf cut by the inner cutter wheel, and each including apair of sloping rock breaker surfaces flanking its cutting edge, saidsurfaces serving to fracture the rock between kerfs.
 3. The combinationof claim 1, wherein said shaft supports at least one additional disccutter wheel which is independently mounted for free rotation about suchshaft.
 4. The combination of claim 3, wherein each said disc cutterwheel comprises a pair of parallel radial side faces, such cutter wheelsare mounted for independent free rotation about the shaft by an annularsleeve type bearing, and an annular radial thrust seal contacts theradial inner portion of each cutter wheel side face, and a seal memberconcentrically surrounds each said thrust washer, each seal memberhaving a radial seal face in sliding sealing contact with the side faceof the cutter wheel.
 5. The combination of claim 4, wherein each sealmember is provided with an annular ring of elastomeric material betweenit and a portion of the mounting means, for cushioning the seal ring andaxially urging it into contact with the side face of the cutter wheel.6. In a rock boring machine including a cutterhead mounted for rotationabout an axis, a center cutter assembly comprising: a fixed shaftextending across the axis of rotation of the cutterhead, a first disccutter wheel mounted for free rotation about said shaft at a locationradially outwardly from said axis of rotation, a second disc cutterwheel mounted for free rotation about said shaft at a location spaced onthe opposite side of said axis of rotation and radially outwardly fromsaid axis a further distance than said first disc cutter wheel, each ofsaid disc cutter wheels comprising a circumferential cutting edgeoriented to cut a kerf along a circular path surrounding the axis ofrotation, and sloping rock breaker surfaces flanking said cutting edge,with the radially inward breaker surface of the first disc cutter wheelbeing spaced close enough to the axis of rotation to effectivelyfracture the center region rock located inside the kerf established bysuch disc cutter wheel, and shaft support means on each side of eachsaid disc cutter wheel.
 7. The combination of claim 6, furthercomprising a third disc cutter wheel mounted for free rotation on saidshaft radially outwardly of said first disc cutter wheel, said thirddisc cutter wheel being spaced radially outwardly from the axis ofrotation a distance fruther than the second disc cutter wheel, and meanssupporting said shaft on each side of said third disc cutter wheel. 8.The combination of claim 7, further including a fourth disc cutter wheeland mounting means therefor situated laterally outwardly from anintermediate portion of said center cutter assembly, including a fixedshaft extending radially of the cutterhead and substantially at a rightangle to the shaft of said center cutter assembly, said fourth disccutter wheel being mounted for free rotation about said second shaft toform a kerf radially outwardly adjacent the kerf cut by the third disccutter wheel.
 9. The combination of claim 8, further comprising a fifthdisc cutter wheel spaced laterally outwardly from said center cutterassembly on the side thereof opposite the fourth disc cutter wheel, andincluding a fixed shaft mounted on said cutterhead to extend radially ofthe cutterhead and substantially at a right angle to the axis of thecenter cutter assembly shaft and substantially coaxially with the shaftfor the fourth disc cutter wheel, said fifth disc cutter wheel biengmounted for free rotation about its shaft so as to cut a kerf radiallyoutwardly adjacent the kerf cut by the fourth disc cutter wheel.
 10. Arock cutting assembly comprising a fixed shaft, a disc cutting wheelmounted for free rotation on said shaft, said wheel including a pair ofgenerally radial side faces, a circumferential cutting edge, and a pairof rock breaker surfaces flanking said cutting edge and intersecting theradial side faces of said wheel, mounting means for said shaft includinga member disposed axially outwardly of each said radial side face, eachsaid member including an annular groove therein opening towards its sideface of the disc cutter wheel, a nonrotating seal member inside eachsaid groove, and an elastomeric material serving to urge each sealmember axially towards its radial face of the disc cutter wheel, saidseal member including a radial seal face making sliding sealing contactwith the radial face of the disc cutter wheel.
 11. The rock cutterassembly of claim 10, comprising a sleeve type plain bearing mountingsaid disc cutter wheel for free rotation about the shaft, and an annularradial thrust bearing supported axially outwardly of each radial sideface of the disc cutter wheel, radially inwardly of the seal members.